Electric translating circuit



Dec. 13, 1932. A 1,891,114

ELECTRIC TRANSLATING CIRCUIT Filed March 30, 1951 In ventor':

Camil ASabbah,

His Attorney.

Patented Dec. 13, 1932 UNITED STATES PATENT OFFICE A GAME A. SAIBBAI-I,or scHENEc'rAnY, NEW YORK, ASSIGNOR To GENERAL ELECTRIC COMPANY, AoonroRArroN on NEW YORK ELECTRIC rnANsLATING oinourr Application filedMarch 30, 1931. Serial No. 526,336.

My invention relates to electric translating circuits and moreparticularly to such circuits utilizing electric valves of the mercurypool cathode type.

5 In many electric translating circuits, and more particularly in suchcircuits adapted to transmit energy from a direct current sup plycircuit to an alternating current load circuit the use of electricvalves of the mercury pool cathode type has beenfoundparticular lyadvantageous because of the relatively large amounts of power which maybe handled at ordinary operating voltages. It is wellknown that thevoltage required to 1 initiate an arc in such a valve is considerablyhigher than the normal voltage drop in the valve when conductive. It hasbecome common practice to provide such valves with auxiliary keep-aliveelectrodes to maintain the cathode in an ionized condition in caseswhere the valve carries current intermittent ly. In certain cases itbecomes necessary to provide means for initiating an arc in the electricvalve, used in such a translating circuit, upon energization of thedirect current circuit, the auxiliary keep-alive electrodes beingenergized thereafter from some portion of the translating circuit.

It is an object of my invention therefore to provide an improvedelectric translating circuit including an electric valve of the mercurypool cathode type in which means is provided for automaticallyinitiating an arc in the valve upon energization of the direct currentcircuit.

It is a further object of my invention to provide an improved electrictranslating circuit energized from a direct current supply circuit andincluding an electric valve of the mercury pool cathode type providedwith auxiliary are maintaining electrodes in which means is provided forimpressing a high transient voltage upon the auxiliaryelectrodes, uponenergization of the direct current circuit, for initiating an arc in theelectric valve. p In accordance withone embodiment of my invention anelectric translating circuit comprising anapparatus for transmittingenergy i from a direct current supply circuit to an al l current loadcircuit, and including a pair of electric valves of the mercury poolcathode type is provided with means for initiating an arc in the valvesupon energization of the direct current circuit. The electric valves areprovided with auxiliary arc maintaining electrodes which are normallyenergized through a transformer from the alternating circuit of theapparatus to maintain the cathodes of the valves in an ionized state. Acircuit including a reactance, such, for example, as an oscillatingcircuit, is connected across the direct currentcircuit of the apparatusand includes circuit interrupting means, which may be a contaotoroperated by a solenoid, the coil of which comprises the reactance. Thecircuit including the auxiliary electrodes and the cathodes of theelectric valves is connected in parallel with the reactance so that thedischarge of the'reactance causes a transient voltage to be impressedupon the auxiliary electrodes. 7 I

For a betterunderstanding of my invention, together with other andfurther objects thereof, reference is had to the follow- 7 ingdescription taken in connection with the accompanying drawing and itsscope will be pointed out in the appended claims. The single figure ofthe accompanying drawing illustrates my invention as applied to an 8ternatir apparatus for transmitting energy from a direct current supplycircuit to an alternating current load circuit. I

Referring now to the drawing, I have illustrated an arrangement fortransmitting 8 energy from a direct current supply circuit 10 to analternating current load circuit 11. This apparatus may be any of theseveral types well known in the art but I have illustrated by way ofexample, an apparatus of the type known in the art as a parallelinverter such as is disclosed and broadly claimed in United StatesLetters Patent No. 1,800,002, granted April 7, 1931, upon theapplication of E. F. V. Alexanderson. This apparatus comprises atransformer l2 havinga secondary winding, connected to the alternatingcurrent circuit 11 and a primary [winding provided with an electricalmidpoint connected to the positive side of the direct current circuitand with two end terminals connected to the negative side of the directcurrent circuit through electric valves 13 and 14. Each of electricvalves 13 and 14 is provided with an anode, a control grid, a mercurypool cathode, and auxiliary are maintaining electrodes 15, which may beof any of the several types well known in the art, although I haveillustrated by way of example auxiliary mercury pools contained in sidechambers of the envelopes of the electric valves. A commutat-ingcapacitor 16 is connected between the anodes of electric valves 13 and14. The auxiliary electrodes 15 of electric valves 13 and 14 areconnected to their respective cathodes through opposite halves of thesecondary windings of exciting transformers 17 and 18, respectively, anda reactance 19 which comprises the onerating coil of an electromagneticswitch 20. The switch 20 is preferably of a quick opening type and asillustrated may be of the mercury type. The control grids of electricvalves 13 and 14 are connected to their common cathode circuit throughopposite halves of the secondary winding of grid transformer 21 and acurrent limiting resistor 22. The primary windings of the transformers17. 18 and 21 are energized from the alternating current circuit, theconnections to the winding of the transformer 21 including a capaci tor23 for determining the frequency of the alternating current delivered tothe c rcuit 11 in case that circuit is not independently energized. Incertain instances it may be desirable to connect a reactance 24 and acapacitor 25 in series with the reactance 19 and switch 20 in order toproduce a transient with the desired characteristics to excite theauxiliary electrodes 15. A high resistance 26 is preferably connectedacross the capaci tor 25 to allow any residual charge to leak off. Ihave shown a conventional switch member 27 by means of which the directcurrent circuit of the apparatus may be energized.

The general principles of operation of the power converting apparatusdescribed above will be well understood by those skilled in the art, ormay be found explained in detail in the above mentioned Alexandersonpatent. In brief, when one of the electric valves 13 or 14 is madeconducting, for example, valve 13, current will flow through theleft-hand portion of the primary winding of transformer 12 producing apotential in the primary winding connected in circuit 11 and in theright hand portion of the primary winding and charging the commutatingcapacitor 16 to substantially twice the direct current po tential of thedirect current circuit. This induced potential impresses a transientupon the grid circuit comprising the primary winding of transformer 21and capacitor 23 and, after a predetermined interval, the grid of theelectric valve 14 is made conductive. Commutating capacitor 16 nowdischarges through the valves 13 and 14 instantly 1nterrupting thecurrent in the valve 13. In this manner current is periodicallytransferred between the valves 13 and 14, producing and alternatingcurrent in the secondary winding of the transformer 12 connected to theload circuit 11. In many cases the potential of the direct currentcircuit will not be sufficient to initiate an are through the valves 13and 14 unless their cathodes are ionized, and, since the alternatingcurrent circuit is not energized until after the valves becomeconductive, additional means must be provided for ionizing the cathodesof the valves 13 and 14. For example, assume that switch member 27 hasjust been closed. A transient of current will flow through the circuitincluding capacitor 25, reactor 24,

switch 20 and reactance 19. This transient current flowing throughreactance 19, which comprises the operating coil of the electromagneticswitch 20, will operate the switch 20 to open its contacts at the sametime interrupting the transient current. Because of the high reactanceof the winding 19, any tendency to interrupt the current flowin thereinsuddenly will produce a high translent voltage. This voltage isimpressed upon auxiliary electrodes 15 of the valves 13 and 14 throughthe secondary windings of exciting transformers 17 and 18 and initiatesan arc from the auxiliary electrodes 15 to the main cathodes of thevalves. This ionization of the cathodes of valves 13 and 14 enables theapparatus to function as described above. The alternating currentsupplied by the circuit 11 to the transformers 17 and 18 maintains thekeep-alive are between the cathodes and the auxiliary electrodes 15 ofthe electric valves. It will be noted that this keepalive current flowsthrough the reactance 19 and thus maintains the contacts of the switchmember 20 open. Any residual charge which may have been upon thecapacitor 25 at the interruption of the current transient in theoscillating circuit will slowly leak off through the resistor 26.

While I have illustrated and described what I at present consider thepreferred embodiment of my invention, it will be obvious to thoseskilled in the art that various chan es and modifications may be madewithout eparting from my invention and I, therefore, aim in the appendedclaims to cover all such changes and modifications as fall within thetrue spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In combination, a direct current supply circuit, a normallydeenergized alternating current load circuit, means for transmittingenergy therebetween including an electric valve of the mercury poolcathode type pro- Vided with auxiliary arc-maintaining electrodes, meansfor initiating operation of the apparatus upon energization of thedirect current circuit comprising reactance means connected to beenergized momentarily and simultaneously therewith and means forexciting the auxiliary electrodes with the discharge of said reactance,and means for normally exciting said auxiliary electrodes from saidalternating current circuit.

2. In combination, a direct current supply.

circuit, a normally deenergized alternating current load circuit, meansfor transmitting energy therebetween including an electric valve of themercury pool cathode type provided with auxiliary are maintainingelectrodes, means for initiating operation of the apparatus uponenergization of said direct current circuit comprising anoscillatorycircuit connected across said direct current circuit and including anelectromagnet and normally closed contacts operatedthereby, and acircuit including said auxiliary electrodes connected in parallel tosaid electromagnet, and means for normally exciting said auxiliaryelectrodes from the alternating current circuit of the apparatus.

In witness whereof, I have hereto set my hand.

CAMIL A. SABBAH.

